Weekly Recap
This week, the eMOLT fleet recorded 133 tows of sensorized fishing
gear.
Bottom temperatures south of Long Island in 14-16 fathoms are in the
upper 40s and low 50s (see the plot below) with surface waters in the
mid to upper 50s. Similar conditions can be found along the South Shore
of Massachusetts.

The southwestern part of Cape Cod Bay has some of the warmest bottom
temps we’re seeing at the moment (in the mid-50s). Heading up to Maine,
east of Penobscot Bay, temps remain in the mid-40s at the bottom (~40
fathoms), with surface temperatures only a degree or two warmer.
George and Huanxin completed a calibration check of the 25 DOT-2
dissolved oxygen and temperature loggers that we have here in the lab.
There were a couple hiccups with one logger that may need to go back to
the factory for more testing. The other 24 successfully detected hypoxic
conditions in the first calibration bath and tracked temperature within
fraction of a degree of the reference probe. If you have a Dissolved
Oxygen probe, we’ll be reaching out with prepaid envelopes to get those
back to us for pre-season calibration checks and new batteries.
The plot below shows our temperature test with one probe. The serial
number of the DOT-2 probe is shown at the top of the plot. The white
circles are a plot of the temperature measured by the Fluke 1523
Calibration Thermometer (x-axis – horizontal) against the temperature
measured by a DOT-2 probe (y-axis – vertical). For example, if the Fluke
1523 read 5 degrees, we would expect the DOT-2 probe to also read 5
degrees. The black line is a 1:1 line, so if the DOT-2 probe performed
flawlessly, all of the points would be on that line. As you can see, it
was slightly off (Root Mean Squared Error of 0.004 degrees C or 0.0072
degrees F) and the estimated relationship between the calibration
thermometer temps and the DOT-2 temps is shown by the dashed red line.
Our highest Root Mean Squared Error was 0.025 degrees C or 0.045 degrees
F.

The second plot that we generated for each logger shows Dissolved
Oxygen concentrations (mg/L) over time as the logger was moved between
different water baths. In the plot below, you can see open circles that
indicate the logger was in air, red circles indicating that the logger
was in the low oxygen bath, and blue circles indicating that the logger
was in the high oxygen bath. The single blue point in the middle is
likely the logger taking some time to equilibrate back to higher
dissolved oxygen levels after being in the low DO bath. In the real
world, loggers are unlikely to go through this rapid of a shift.
